Question: Divide the following complex numbers: $\dfrac{9 e^{7\pi i / 12}}{3 e^{11\pi i / 6}}$ (The dividend is plotted in blue and the divisor in plotted in green. Your current answer will be plotted orange.)
Answer: Dividing complex numbers in polar forms can be done by dividing the radii and subtracting the angles. The first number ( $9 e^{7\pi i / 12}$ ) has angle $\frac{7}{12}\pi$ and radius 9. The second number ( $3 e^{11\pi i / 6}$ ) has angle $\frac{11}{6}\pi$ and radius 3. The radius of the result will be $\frac{9}{3}$ , which is 3. The difference of the angles is $\frac{7}{12}\pi - \frac{11}{6}\pi = -\frac{5}{4}\pi$ The angle $-\frac{5}{4}\pi$ is negative. A complex number goes a full circle if its angle is increased by $2 \pi$ , so it goes back to itself. Because of that, angles of complex numbers are convenient to keep between $0$ and $2 \pi$ $-\frac{5}{4}\pi + 2 \pi = \frac{3}{4}\pi$ The radius of the result is $3$ and the angle of the result is $\frac{3}{4}\pi$.